For battery-operated portable equipment, rechargeable batteries are usually used as an offline power source. A battery power management system is needed to deliver power from either an external DC source or from a rechargeable battery to the equipment. When the external power source is available, it provides regulated power for the load and charges the battery (external mode). When the external power source is unplugged, the battery is then switched to be the power source (battery mode). A conventional realization may use a battery charger for charging the battery and another voltage regulator for power regulation. A power multiplexer is also needed to switch between the power sources. Switching converters are usually employed to implement the battery charger and the voltage regulator due to their high efficiency. As a result, a battery power management system may require a few switching converters and power multiplexers for switching between power sources and to generate multiple regulated power supplies.
Among existing multiple-supply implementations, a single inductor multiple-output (SI-MO) switching converter is a very cost-effective solution. Only one off-chip inductor is required to provide multiple regulated outputs. Low cross-regulation can be achieved by employing time-multiplexing (TM) control that works in discontinuous conduction mode (DCM) or by allowing the inductor current to work in pseudo-continuous conduction mode (PCCM) with freewheel switching control. Power multiplexers are then used to switch among the various power sources in the battery power management system.
A battery power management (BPM) system has two functions: power regulation and battery charging. Prior BPM systems consist of individual power regulators and battery charger, and power multiplexers are used to switch among the power paths. The battery charger could be a linear regulator, but a switching converter is often used for its high efficiency such that no heat sink is needed. Similarly, switching converters are usually used for power regulation due to their high efficiency over a wide loading current range, and that they can implement voltage step-up, step-down and inversion. Hence, for a high-efficiency BPM system with one battery and one regulated output, two switching converters using two inductors are needed. Moreover, a power multiplexer consists of two power switches is used to switch between the two power sources. Therefore, the BPM system requires at least two inductors and six power switches.
As a result, an integrated solution to perform power path control and multiple-output power regulation is desirable for reducing the PCB (printed circuit board) area, system complexity and overall production cost.